Process of preparing leuco-1.4-dihydroxyanthraquinones



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Patented Aug. 16, 1932 UNITED STATES PATENT I JAMES OGILVIE, or BUFFALO, AND DONALDIG. ROGERS; or HAMBURG, NEw'Y o-mrf assrenoas T0 NATIO1\TAL ANILINE& CHEMICAL.- GQMIBANY, me, or 'imw Yon-x;

-11. Y.,.A coaroa a'rlon' OF NEW YORK PROCESS "PREPARING: LEUCO-lA-DIHYDROXYANTHRAQUINONES This invention relates to improvements in the process ofprep aring leuco-lxl-dihydroxyanthraquinones from 2-haloge'n (3-halogen) 1.L-dihydroxyanthraquinones. It relates particularly toimprovements in the preparation of leuco-quinizari-ne from 2 chloro (3- chl0ro)-quinizarine. a p a An object of the present invention is to produce a leuco-1.i-dihydroxyanthraquinone (herein referred to as a leuco-quinizarine) from a2-halogen (3-halogen) -1.t-dihydroxy. anthraquinone (herein referred to as an ortho-ha-logen-quinizarine) by a process which requires only a relatively short period of time for its completion.

Another object of the invention is to provide a process for the production of a leucoquinizarine by a reduction ofa'n ortho-halo: gen-quinizarine in an alkalinemedium;

Other objects of the invention will in part. lip-obvious and will in part appear hereina ter.

It has been proposed to prepare leuco quinizarine by heating 2-chloro (3-chloro)- 1.4-dihydroxyanthraquinone' (herein referred to-as chloroquinizarine) solution in a suliuric-boric acid mixture with a finely di-- vided metal powder. It also has been proposed to prepare leuco-quinizarine from quinizarine (1.4:-dillydIOXYLIltliIfiQlliIiOIIG) by the. action of a metal on quinizarine in an acid solution, by the action of alkaline hydrosulfite on quinizarine in an alkali-nesoliition, and by the action of a finely divided metal and an organic acid on quinizarinein solu-' tion in an inert organic solvent. It is known, I

furthermore, to prepare leuco-quini'zari'ne,

from purpurin [1.214 '(1.3.4:)-trihydroxy an thraquinone'] by the action of a finely divided metal on purpurin in an acid, neutral, or slightly alkaline solution. The reductionof purpurin in alkaline solution'by means of sodium amalgam, stannous salts, or alkaline hydrosulfite, however, d'oes'not produce leuco-' quinizarine, but leads, to the formation of Xanthopurpurin (1.3-dihydroxyanthraquin- The preparation of leuco-quinizarine': from chloroquinizarine by the action of a finely divided metal powder on a solution'of chloro- Application filed November 20, 1929; Serial No. 408,664.

quinizarine in a sulfuric-boric acid mixture 15 ob ectionable,ow1ng to the requirement ofv careful low temperature control, the relat ve-- 1y long period of time required for the completion of the reaction, and thefoamingwhich occurs.

The invention accordingly comprises the] several steps and the relation of one orn-iore of such steps with respect to each o'fthe others v droxyanthraquinone (a leuco-quinizarine) can be obtainedfrom a 2-halogen (3-ha-logen) -IA-dihydroxyanthraquinone (an orthohalogen-quinizarine) by subjecting it to a reducingactionin an alkaline medium, and

the present invention comprisesthe applica-V tion of this discovery to. the preparation of a. leuco-quinizari'ne from an ortho-haloge'n quinizarine. p I

In the practice of the invention an orthohalogen-quinizarine in solution or suspension in an alkaline medium may beheated with-a reducing agent, for example, a hydrosul fit'e, until the reduction is complete. 7 The solution may thenbe' mad'e'acid with an; acidic substance, or a salt may be" added to it, whereupon a,leuco-l.4-dihydroxyanthraquinone ("a leuco-qui'ni zarine) may be obtained as a pre=' cipitate. The precipitate may be filteredofl, washed and dried. It; may be further purified by recrystallization from a suitable" solvent. 7 V p v I Among the halogen-qumia-arines which may be treated in accordance with the invention, there are-included the substitutedand the unsubstituted 2-halogeir ('3-hal0gen-)-1.4-"

dihyd'roxyanth-raquinones, particularly the orthdhaIOgen-q'uinizarines which may"b"e represented by thefollow-ingformula as, -Clor-Br), A represents a hydrogen atom radical, such as, -OH, -SO H, etc.; e. g., 2-

7 DOUG chloro (3-chloro)-1.4-dihydrox anthraqui- (chlordquinizarine);

(bro mo-quinizarine) 2-chloro (3-chloro) -1'.4.7'.8-

tetrahydroxyanthraquinone (chloroquinali zarine); bromoquinalizarine 2-chloro or 2- bromo-, (3-chloro-, or 3-bromo) -1.4 .5.8-tetrahydroxyanthraquinone; Q-chloroor 2- bromo-, (3-'chloro+,. or 3'-bromo-) -1.4.5.8 tetrahydroxyanthraquinone-6-sulfonic acid; 2-chloro-, or 2-bromo-, -alizarine pentacyanine (1.4.5.7.8-pentahydroxyanthraquinone) etc. It is noted that when the halogen-quinizarine containsadditional halogen or sulfonic acid substituents in the beta-position, these may also be replaced by hydrogen during there'action. The alkaline. medium is preferably a dilute solution of a caustic alkali, and may be used'in excess of the amount required to form an alkali-metal salt of the halogen-quinizarine, The reducing agent, as for example, a hydrosulfite (e. g., sodiumhydrosulfite), a stannous salt (e. g., sodium stannite), etc., is preferably employed in considerable excess in order to bring about a com lete reduction. I 7

$1811 the'step' of acidifying the reduced solution is employed as a part of the procedure, any suitable acidic substance may be used, suchas an acid or an acid salt; e.,g., sulfuric acid, hydrochloric acid, sodium acid sulfate, sodium acid sulfite, etc. When the step of adding a salt to the solution is employed, any suitable salt which will salt out the leucoquinizarine from-its solution may be used;

e. g., sodium sulfate, sodium chloride, etc. The procedure in which an acidic substance 1S added to the reduced solution is preferred, however; and the stronger acids areemployed in preference to the weaker acid salts, inasmuch as they tend to leave a smaller amount of undehalogenated material in the final product.

If desired, the leuco-quinizarine maybe oxidized directly to quinizarine without isolation from the reaction mixture, e. g., passing air through the mass upon completion of the reduction untiLthe oxidation is complete, neutralizing with dilute acid, filtering off the quinizarine, washing and drying.-

As an illustrative embodiment of a'mannor in which the invention may be carried into practice-the following example is presented. The parts are by weight.

Example: 100 parts of 2 chloroquinizarine in the form of apasteis 'inixed with 7,000

parts of water, and 150 parts of sodium hydroxide in the formof a*50% aqueous solution is added with agitation. The mixture is heated to boiling, and when substantially all ofthe 2-chloroquinizarine "has apparently r o. bromo) -1.4-dihydroxyanthraquinone' gone into solution, about 160 to 200 parts of sodium hydrosulfite (100% or its equivalent) is added. Reduction appears to take place immediately, the color of the solution changing from a deep bluish violet to bright yellow. Boiling is continued for about ten minutes to insure completion of the reaction,

heating is then interrupted, and the mixture 1,isv added at once toabout 300.parts of dilute sulfuric acid (50%). Leuco-quinizarine precipitates in, .the .form of brownish-yellow granules. It is filtered off, washed acid-free with water, and dried The crude product thus obtained is in the form of a yellow solid which,'on analysis, shows a chlorine content of approximately 0.2 per cent. .Upon recrystalli'zing from toluene or dichlorobenzene, apurified leuco-quinizarine melting at about 151 C. is obtained.

It'will be evident that the invention is not limited tothe details of the foregoing specific example,but that the process may be varied within wide limits without departing from the spirit and scope of the claims.

Thus, the invention is not limited to the treatment of chloroquinizarine but is generally applicable to the treatment of other ortho-halogen-quinizarines; i. e., lA-dihydroxyanthraquinone compounds which contain a halogen substituent in the 2-(3-) position. Other alkalis may be employed instead of sodium hydroxide, and the strength and amount may vary. It is desirable in practice, however, to employ at least suflicient alkali to form an alkali-metal salt of the chloroquinizarinen Instead of sodium hydrosulfite, other alkali-metal hydrosulfites or a mixture of substances which will generate hydrosulfite under the reaction conditions (such as, zinc and sodium bisulfite) may be employed. Furthermore, the hydrosulfite need not be addedtothe boilingalkaline solution of the chloroquinizarine, but they may be mixed at another point in the procedure; e. g., before the solution is heated. The reaction is preferably carried out at the boiling point of the solution, although other temperatures may be used.

Acidic substances other than sulfuric acid may be added to the reduction mixture to produce a precipitate of the leuco-quinizarine, e. g., hydrochloric acid, sodium bisulfite, sodium bisulfate, etc., or the leuco-quinizarine may be salted out from the reduction mixture by means of a suitable salt, such as, an alkalimetal sulfate, sulfite, chloride, etc.; e. g., sodium sulfate, sodium sulfite,

formed can be caused spontaneously to separate from the reaction mixture by the sodium bisulfite produced as a result of the reduction.

I The present invention thus makes possible sodium chloride, 1 etc; By carrying out the reduction with an e the production of a leuco-quinizarine by an alkaline reduction of an ortho-halogen-quinizarine, and is superior to the process heretofore known for the reduction of an orthohalogen-quinizarine in that it does not require a long period of time for its completion, or careful low temperature control, and entails no difiiculties from foaming.

Since, in carrying out the above process, certain changes may be made'without departing from the scope of the invention, it is intended that all matter contained in the above description shall be interpreted as illustrative and not in a limiting sense.

It is also to be understood that the following claims are intended to cover all of the generic and specific features of the invention herein described and all statements of the scope of the invention which, as a matter of language, might be said to fall therebetween.

We claim:

1. The process of preparing a leuco-quinizarine which comprises reducing an orthohalogen-quinizarine in an alkaline medium.

2. The process of preparing a leuco-quanizarine which comprises heating an orthohalogen-quinizarine with a reducing agent in an alkaline medium.

3. The process of preparing a leuco-quinizarine which comprises reacting an orthohalogen-quinizarine in an alkaline medium with a hydrosulfite.

4. The process of preparing a leuco-quinizarine which comprises reacting an orthohalogen-quinizarine in an alkaline medium with a stannous salt.

5. The process of preparing a leuco-quinizarine which comprises heating an alkaline solution of an ortho-halogen-quinizarine with an alkali-metal hydrosulfite.

6. The process of preparing a leuco-quinizarine which comprises reacting an orthohalogen-quinizarine in an alkaline medium with a hydrosulfite, and acidifying the resulting reaction mixture.

7. The process of preparing a leuco-quinizarine which comprises reacting an orthohalogen-quinizarine which corresponds with the probable formula 8. The process of preparing a leuco-quinizarine which comprises heating an alkaline solution of an ortho-halogen-quinizar1ne which corresponds with the probable formula.

- v V V i V v in which a represents a halogen atom, A represents a hydrogen atomor a hyroxyl group, and B represents a hydrogen atom, a halogen atom, or an inorganic radical, with an alkalimetal hydrosulfite,

9. The process of preparing a leuco-quiniZarine'which comprises reacting an orthohalogen-quinizarine which corresponds with the probable formula: i

A O OH B V n A O OH i i H in which '00 represents a halogen atom, A

resents a hydrogenatom or al'iydfroxyl group, and B represents a hydrogen atom, ahalogen atom or an inorganic radical, in an aqueous caustic alkali solution, with a stannous salt, and treating the resulting reaction mixture with an acidic substance.

, 11. The process of preparing a leuco-quinizarine which comprises reducing chloroquinizarine in an alkaline medium.

,12 The process of preparing a leuco-quiniZarine which comprises reducing chloroquinizarine in an alkaline medium with a hydrosulfite.

13. .The process of preparing leuco-quinizarine which comprises heating an aqueous caustic alkali solutionof chloroquinizarine with sodium hydrosulfite. 3 1

14.v Tha-process which comprises heating an aqueous caustic alkali solution of chloroquinizarine with sodium stannite, and aciditying the resulting reacton mixture, whereby leuco-quinizarine is produced.

15. The process of preparing leuco-quinizarine which comprises heating an alkaline solution of chloroquinizarine with sodium hydrosulfite, and mixing the resulting reactionmixture with dilute sulfuric acid.

k nizarine which comprises reducing nizarinb 16. The process which comprises reducing an ortho-halogenquinizarine 111 an alkaline medium, oxidizing the leuco-quinizarine thus and separating the quinizarne. e

17. The process whch comprises reducing chloroquinizarine by heating in an alkaline medium with a hydrosulfite, oxidizing" the leuco-quinizarine thus formeddirectly to quinizarine by means of air,neutralizing with a dilute acid, and separating 'the quinizarine.

18. The process whch comprises heating to boiling in an alkaline medium an ortho-halogen-quinizarine and a hydrosulfite in the proportion corresponding to parts of chloroquinizarine to about 1160 to 200 parts of sodium hydrosulfite, and acidifying the reaction mixture, whereby leuco-quinizarine is produced.

V 19. The process which comprises heating formed directly to quinizarine, neutralzing,

100 parts of 2-chloroqu1nizarine with at least 160 parts or" sodium hydrosulfite in an excess of dilute aqueous caustic alkali solution until thechange in color of the reaction mixture ceases, mixing an excess of an acidic substance with the resulting reaction mixture to render it acidic, and separating the leuco-quinizarine thereby produced.

20. The process which comprises admixing,

100 parts of 2-chloroquinizarine in the form,

of a paste with 7000 parts of water, adding about parts of sodium hydroxide in the form of an aqueous solutionand heating to boiling until a solution is formed, then addn in? about to 200 parts of sodium hydrosu fi te, boiling to insure completion of the reaction, ac difying the reaction mixture with dilute sul uric acid,'and eparatng the leucoquinizarine thereby produced.

- 21. The process of preparing a leuco-quian orthohalogen-quinizarine an alkaline medium, and treating the resulting reaction mixture with an acidic substance. 7

QQflQhe process-of preparing a leuco-quiwhich comprises heating an orthohQ Og H-qQ nZarine with a reducing agent in an alkalin edium, and acidifying the resulting reactiommixture.

he process qf preparing leuco-quinizarine which comprises heating an aqueoussodium hydroxide solution'of 2.-c=hloroquini- Zar1ne wlth sodium hydrosulfite, and acidifying the resulting reaction mixture with dilute sulfuric acid.

In witness whereof, we have hereunto set our hands.

JAMES oGILVIEQ DONALD o. ROGERS. I 

